Mixture Of Iron Oxides Research Articles

Microwave Processing of Low-Grade Banded Iron Ore with Different Reductants

The current study investigates the effect of microwave processing on low-grade banded iron ore using charcoal, coking coal, and non-coking coal. Charcoal showed better microwave heating response at low temperatures, and the coals exhibit better heating response at higher temperatures. Low carbon dosage ~ 12% is sufficient to generate concentrate with 61.8% iron grade and ~6% for 94.8% iron recovery comprising of magnetite phase suitable for iron-making applications. The process separation efficiency of ~ 95% is achieved at 6% carbon dosage and decreases with an increase in carbon due to formation of the fayalite phase. The metallization degree showed a strong dependency on reductant dosage and achieved a maximum value of 22.7% at 18% charcoal. The comparison of ore with pure iron oxide and the synthetic mixture of iron oxide indicated that the underlying bonding due to banded structure enhances the Joule heating during microwave irradiation and thereby aids in attaining higher temperature and better separation.

Study of the formation of ferrihydrite under prebiotic chemistry conditions: artificial seawater 4.0 Gy and ammonium thiocyanate

AbstractAmong the several steps involved in molecular evolution, molecular preconcentration is the first and most important. If the molecules are not preconcentrated the other steps of molecular evolution cannot occur. There are several ways to preconcentrate molecules: sorption, wetting/drying cycles, freezing/sublimation and sorption/precipitation with minerals. In the present work, the effect of NH4SCN and artificial seawater 4.0 Gy on the synthesis of ferrihydrite was studied. It should be noted that thiocyanate could play the same role as that of CN− in the Strecker reaction. Unlike today's seawater that has high Na+ and Cl− concentrations, the seawater used in this work has high Mg2+, Ca2+ and SO42− concentrations. Two results stand out, first SCN− and NH4+ were preconcentrated by sorption/precipitation in some syntheses and second, in some experiments, a mixture of goethite, hematite and magnetite was obtained. The sorption/precipitation of SCN− is always associated with the synthesis of goethite. This could be an indication that SCN− interacts with Fe3+ through the sulphur group of SCN−. In addition, the synthesis of magnetite could be an indication that the SCN− ion oxidized, forming thiocyanogen-(SCN)2 or trithiocyanate ion-(SCN)−3 and that Fe3+ reduced to Fe2+. Besides the sorption/precipitation of SCN− and NH4+, Fourier-transform infrared spectroscopy also showed that sorption/precipitation of SO42− and CO32− occurred. Ferrihydrite synthesized with artificial seawater presented the highest surface area and pore size. The pHpzc values of the samples were in the range of pHpzc described in the literature. The X-ray photoelectron spectroscopy (XPS) measurements performed show proportions of iron present in different oxidation states, however, the electronic similarities observed in the mixtures of iron oxides and oxy-hydroxides make it difficult to quantify them. Direct comparison between XPS spectra of the Fe2p and O 1s core-levels reveal no significant differences from the effect of artificial seawater 4.0 Gy on the synthesis of ferrihydrite.

The results prediction of iron oxides aluminothermy

"The paper presents the results and conclusions of the statistical processing of data on aluminothermic reduction reactions of iron oxides. Starting from the thermodynamic and chemical information regarding the aluminothermic reduction reactions of the iron oxide mixtures, their thermal and chemical effects were estimated and the information thus obtained was statistically processed. The results obtained by statistical processing of information obtained by theoretical reasons, presented in the form of regression equations or their graphical expressions, can be used to effectively determine the optimal phase composition of thermit kits based on iron oxides and forecast the value of reaction heat, resulting from the actual reactions development. The practical application of these results was ensured by the company QUARK IMPEX SRL, one of the main producers and users of thermit welding kits for rail joints by aluminothermal welding, in Romania. "

Iron coral: Novel fungal biomineralization of nanoscale zerovalent iron composites for treatment of chlorinated pollutants

In this research, a facile fungal biomineralization method was developed for the synthesis of nanoscale zerovalent iron (nZVI) with a unique N-doped branching structure, which showed excellent stability and mediated high degradation of carbon tetrachloride (CCl4) in aqueous solution. The ureolytic fungus Neurospora crassa was cultured in medium containing Fe2+ and urea which resulted in iron carbonate biomineral precipitation. Following carbonization at 900 °C, the fungal-carbonate composite became highly porous and granular nanoparticles (~50 nm diameter) were distributed evenly around the carbonized hyphae in a coralline manner. This ‘iron coral’ composite was identified as a mixture of zerovalent iron (Fe0), carbon iron (Fe1.91C0.09) and iron oxide (Fe3O4). The porous branching hyphal framework improved the capture efficiency of CCl4, and the N-doped sites may accelerate the electron transfer between CCl4 and nZVI. Geochemical simulation was applied to verify the formation of the biominerals, and chemical analyses confirmed its significant degradation ability for CCl4. These findings have therefore demonstrated that ureolytic fungi can provide a promising environmental-friendly system for the novel preparation of nZVI through biomineralization with the resulting ‘iron coral’ capable of significant removal of a chlorinated compound and therefore indicating new bioremediation applications.

Decomposition of Ammonium-Perchlorate-Encapsulated Nanoscale and Micron-Scale Catalyst Particles

Iron oxide is the most common catalyst in solid rocket propellant. Increased performance of propellant by encapsulating iron oxide particles within ammonium perchlorate (AP) has been previously demonstrated, but only nanoscale particles were used, and encapsulation was only accomplished in fine AP ( microns in diameter). In this study, the size of the particle inclusions were extended to micron scale within the AP particles, and the particle sizes of the AP-encapsulated catalyst particles were increased to the coarse region (hundreds of microns). Fractional crystallization techniques were used with fine AP-encapsulated particles acting as nucleation sites for precipitation. This paper reports catalyst particle inclusions of micron scale, as well as nanoscale, within AP and presents characterization of this encapsulation. Encapsulating micron-sized particles and growing these composite particles could pave the way for numerous possible applications. A study of the thermal degradation of these AP-encapsulated particles compared against a standard mixture of iron oxide and AP showed that AP-encapsulated micron-scale catalyst particles exhibited similar behavior to AP-encapsulated nanoscale particles. Using computed tomography, it was found that catalyst particles were dispersed throughout the interior of coarse AP-encapsulated micron-scale catalyst particles and decomposition was induced within these particles around catalyst-rich regions.

Plasma-catalytic conversion of CO2 to CO over binary metal oxide catalysts at low temperatures

Non-thermal plasma (NTP) technology is gaining increasing interest for CO2 conversion due to its potential to convert inert and stable CO2 to value-added fuels and chemicals at ambient conditions. Combining catalysts with plasma can enhance conversion and energy efficiency simultaneously, overcoming the trade-off barrier commonly present in plasma processes. This work reports the influence of various ceria-promoted iron oxide catalysts on the decomposition of CO2 to carbon monoxide and oxygen in a packed bed, dielectric barrier discharge (DBD) reactor at low temperatures and ambient pressure. As ceria is an expensive rare earth metal, its combination with a cheap, abundant metal such as iron can make the process far more economical. The optimum CO2 conversion (24.5%) and energy efficiency (13.6%) were achieved using γ-Al2O3 supported 5Fe5Ce, almost twice the conversion attained using 10Fe (13.3%). Catalysts were characterized using N2 adsorption, X-ray diffraction (XRD), Raman spectroscopy, H2-temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) analysis. A solid solution formed from the mixture of iron oxide and ceria. A critical concentration of iron oxide is required to increase the number of oxygen vacancy sites in the solid solution. The synergy between Fe and Ce, and thus the oxygen vacancy sites, can also be optimized via the synthesis method. A reaction mechanism has been proposed for CO2 conversion at the catalyst surfaces.

Phosphate competition with arsenate on poorly crystalline iron and aluminum (hydr)oxide mixtures

Phosphate competes with arsenate for sorption sites on poorly crystalline iron and aluminum (hydr)oxides. The competition has implications e.g. for the management of arsenic-contaminated soil and water. Phosphate competition with arsenate on mixed phases containing both iron and aluminum (hydr)oxides has rarely been investigated. Here, the phosphate competition with arsenate on mixtures of poorly crystalline aluminum hydroxide (Alhox) and ferrihydrite (Fh), was investigated in batch experiments at pH 6.5. X-ray absorption spectroscopy (XAS) was performed on the phosphorus and arsenic K edges, which offered a unique insight in the partitioning of arsenate and phosphate on mixed Alhox-Fh sorbents. Under the studied conditions the sorption capacity of the mixed sorbents (per mol Al or Fe) increased at higher Alhox to Fh ratios. The XAS measurements provided direct evidence that phosphate competed more effectively with arsenate for sorption sites on Alhox than on Fh. For example, in a mixture with 50% of both sorbents and with similar additions of arsenate and phosphate, 71% of the oxyanions adsorbed on Fh and 46% on Alhox were arsenate. Consequently, phosphate may mobilize arsenate more easily from mixed iron-aluminum matrices that are rich in aluminum.

The Application of Quasi-Elastic Neutron Scattering to Investigate Hydrogen Diffusion in an Iron-Based Fischer\u2013Tropsch Synthesis Catalyst

Iron-based Fischer–Tropsch synthesis (FTS) catalysts evolve in situ on exposure to synthesis gas (CO & H2) forming a mixture of iron oxides, iron carbides and carbonaceous deposits. Recently, the application of inelastic neutron scattering has shown the progressive formation of a hydrocarbonaceous overlayer during this catalyst conditioning period. The evolving nature of the catalyst alters the proportion of phases present within the catalyst, which may influence the transport of hydrogen within the reaction system. Preliminary quasi-elastic neutron scattering (QENS) measurements are used to investigate hydrogen diffusion within an un-promoted iron FTS catalyst that has experienced varying levels of time-on-stream (0, 12 and 24 h) of ambient pressure CO hydrogenation at 623 K. Measurements on the catalyst samples in the absence of hydrogen show the unreacted sample (t = 0 h) to exhibit little increase in motion over the temperature range studied, whereas the t = 12 and 24 h samples exhibit a pronounced change in motion with temperature. The contrast is attributed to the presence of the afore-mentioned hydrocarbonaceous overlayer. Measurements on the samples in the presence of liquid hydrogen show hydrogen diffusional characteristics to be modified as a function of the catalyst conditioning process but, due to the complexity of the evolving catalyst matrix, the hydrogen motion cannot be attributed to a particular phase or component of the catalyst. Problems in the use of hydrogen as a probe molecule in this instance are briefly considered. Coincident neutron diffraction studies undertaken alongside the QENS measurements confirm the transition from hematite pre-catalyst to that of Hägg carbide during the course of extended times-on-stream.

Optimal microwave heating of biochar containing iron ore pellets

Process of microwave heating of a composite material consisting of a mixture of iron oxides (Fe2O3 / Fe3O4), a binder (bentonit), and a carbon-containing powder (biochar) was studied theoretically and experimentally. The values of complex permittivity and permeability of the samples under study were found according to effective medium approximation and enhanced Bruggeman expression in particular. Spatial distribution of temperature in the pellet of composite material was obtained when heated by an electromagnetic field with a frequency of 2.45 GHz, as well as the time dependencies of sample surface temperature.

Transition States for Shock Induced Chemical Reactions in Binary Energetic Materials

In this paper, numerical simulation of shock induced chemical reactions of a thermite mixture of binary energetic material, aluminum and iron oxide, are discussed. To initiate the chemical reactions, the impact or the shockwave should supply the energy to take the reactants, aluminum and iron oxide, to the transition state. Thus, for any numerical simulation of the shock or impact induced chemical reaction in a continuum or mesoscale, it is necessary to identify the transition state. The transition state for the thermite mixture, of aluminum and iron oxide, is identified in this paper and a result from a numerical simulation of the shock induced chemical reaction, in a continuum scale is presented.

Comparative study of low-grade banded iron ores for iron recovery

Two low-grade banded iron ores are evaluated as a potential source for meeting the iron/steel demand due to the scarcity of high-grade iron ores. The present study investigates the processing and enrichment of banded iron ores and their comparison with pure iron oxide and synthetic mixture. The feasibility of physical beneficiation, microwave processing, and carbothermal reduction is thoroughly investigated. A trace amount of magnetite in BHJ ore leads to an improved response of microwave exposure compared to pure iron oxide and mixture. Physical beneficiation was found futile in recovering iron values. The energy consumed during the microwave processing is calculated as 405.2 kWh/ton, whereas for conventional reduction is 223.7 kWh/ton. Significant iron enrichment was achieved through structural alteration of the ore. The microwave processing offered faster reduction kinetics and ferrite formation in a short duration. BHJ sample was found suitable for extracting iron values compared to BHQ using carbothermal reduction.

Effective fluoride adsorption using water hyacinth beads doped with hydrous oxides of aluminium and iron

In this study, the effectiveness of water hyacinth beads doped with hydrous aluminium oxide (WH-HAO), hydrous iron oxide (WH–HFO) and hydrous aluminium oxide-iron oxide mixture (WH-HAO-HFO) was investigated for the removal of fluoride from aqueous solution in batch and fixed bed column systems. The effect of solution pH, initial fluoride concentration, flow rate, bed depth, and competing ions were studied. The adsorption capacities of the adsorbents were 4.43, 4.25, and 4.18 mg/g F for WH-HAO, WH-HAO-HFO and WH-HFO, respectively. Increasing solution pH had the effect of reducing fluoride adsorption, with the effect less pronounced for adsorption using WH-HFO adsorbent. Equilibrium modelling showed that the data better fitted the Freundlich isotherm compared to the Langmuir isotherm, which was consistent with the heterogeneous, rough and porous physical surface indicated by scanning electron microscope (SEM) characterization. Column sorption studies revealed that the breakthrough point was reached earlier at higher inlet fluoride concentration, lower flow rate and lower adsorbent bed depth. The maximum fluoride adsorption capacity of the adsorbent decreased with increasing flow rate and increasing inlet fluoride concentrations while the volume of fluoride solution treated before saturation was found to increase with increasing bed depth and flow rate. Competition to fluoride adsorption followed the order HCO3->PO43->SO42-. Adsorbent regeneration studies showed that at least 80% F adsorption was achieved in 3 sorption-desorption cycles using WH-HAO beads, and NaOH was the most effective desorption agent, achieving >80% desorption of previously adsorbed fluoride in 3 h. Water hyacinth doped with hydrous metal oxides and immobilized in alginate showed great potential for further exploration as adsorbent for the removal of fluoride from water in continuous flow systems.

Iron ore as precursor for preparation of highly active χ-Fe5C2 core-shell catalyst for Fischer-Tropsch synthesis

This work describes a novel method for the preparation of active and stable Fe-based catalyst from an iron ore, which was chemically treated with oxalic acid to obtain a mixture of iron oxides and oxalate. It was found that under CO atmosphere at 350 °C, this mixture can be effectively transformed into active iron carbide phase (χ-Fe5C2), which is highly desirable for FTS. The catalysts were characterized by SEM, TEM, TGA, Raman, XRD, BET, and CO-TPR-MS. The catalytic performance was evaluated under FTS conditions (280 °C, H2 / CO = 1, P =20 bar) and GHSV = 12 N L gcat−1 h−1 for 100 h. The results showed that the CO conversion (66.8%) was higher on the oxalic acid-treated iron ore than in the untreated iron ore (46.5%), obtaining a high C5+ hydrocarbon selectivity (> 60.0%) in all cases. The proposed method significantly reduced the catalyst preparation steps using an inexpensive and abundant raw material for the sustainable preparation of very active and stable Fe-based catalysts for the FTS.

Effect of High Energy Ball Milling Washing Process on Properties of Nd<sub>2</sub>Fe<sub>14</sub>B Particles Obtained by Reduction-Diffusion

Nd2Fe14B particles were obtained from mixture of neodymium oxide, iron oxide, boric acid and CaH2 by reduction-diffusion process. Two different washing processes were used for the separation of magnetic particles from Ca and CaO matrix: usual washing with water and planetary ball milling process in ethanol media. Nd2Fe14BHx hydrogenated state was formed after usual washing with water. Ethanol planetary ball milling washing procedure prevented the formation of Nd2Fe14B hydrides during washing. Variation of milling parameters allowed producing particles with different morphology such as spherical or flakes after planetary ball milling washing process. Influence of milling parameters on magnetic properties of Nd2Fe14B powder was investigated.

Fabrication and characterization of a novel lightweight adiabatic refractory composite consisting of alkaline earth silicate fibers and SiC particles

A novel lightweight adiabatic refractory material combining alkaline earth silicate (AES) fiber board and SiC particles was fabricated by immersing the AES fiber board into a slurry consisting of SiC particles with a median diameter of 1.2 μm and 13% silica-sol as an inorganic binder. When the composite was heated at 1400 °C for 8 h, the fired shrinkage of the composite was almost 0%, while that of untreated AES fiber board was 3.2%. The compressive strength of the composite heated at 1300 °C for 8 h was greatly improved to 0.95 MPa, 4.6 times that of untreated AES board. The corrosion resistance of the composite to a mixture of iron (II) oxide and sodium carbonate at 1400 °C was improved by more than 40% compared to that of untreated AES fiber board.

Использование спеченного сорбента для удаления сероводорода из отходящего промышленного газа при грануляции металлургических шлаков

Authors suggest removing hydrogen sulfide from the hot industrial gas at temperatures 200-300 °C and its subsequent interaction with Fe2O3. For this purpose the following sorbents have been proposed: a mixture of iron oxide and fly ash; iron oxide and pumice; different samples of red mud (bauxite treatment residues containing iron oxide). To prevent dusting and loss of absorbing capacity, the sorbents were shaped into porous granules with other metallic oxides. Materials utilized in the study were obtained the following way: mixing of Fe2O3 with fly ash; sintering of the mixture with red mud. The blend contains aluminum oxide and silica, which can act as matrix shapers, alkali oxides and fluxing agents that reduce the temperature during metal sintering. After the samples had been saturated with sulfur, they were positioned in a venting reservoir, where under the temperature 600-700 °C desorption to the initial state occurred by means of passing an air flow through the sorbent layer. In the process of this operation, sulfur dioxide was released and reactive metal oxides re-emerged. Desorption also generated a small amount of elemental sulfur and sulfuric acid. Absorbing capacity was assessed at higher temperatures, efficiency of H2S removal reached 95-99.9 %. Proposed technology of air cleaning is recommended to use in metallurgic processes with elevated atmospheric pollution, e.g. granulation of melted blast-furnace slag.

Colourful earth: Iron-containing pigments from the Hellenistic pigment production site of the ancient agora of Kos (Greece)

The red, brown, yellow and green pigment lumps from the Hellenistic pigment production site of the ancient agora of Kos (Dodecanese, Greece) are the focus of this paper. A selection of pigments is examined through a combination of analytical techniques, including SEM-EDS on uncoated samples, X-ray powder diffraction, FTIR and pRaman spectroscopy. Through the study of raw pigments deriving from the context of a production site, the aim is to approach pigment manufacturing contextually during the Hellenistic period. The examined red pigments were characterised as red earths (rubricae, μίλτοι), with their colour primarily attributed to hematite. However, significant variance was observed in their chemical and mineralogical composition, reflecting on their final colour. Interestingly, two of the red samples contained lead tetroxide in addition to hematite. The colour of the brown pigments was attributed to a complex mixture of iron oxides. The chemical and mineralogical composition of the two yellow lumps showed that they are of different origin; the first, composed of goethite and quartz, can be characterised as a yellow earth (sil, ὢχρα) and the second corresponds to the mineral jarosite. A green-coloured lump was characterised as a type of celadonitic rock. The variance in the composition of the examined pigments indicates the treatment techniques carried out at the site and the preferences of the local craftspeople. The finds from the Koan workshop illustrate the complex and sophisticated nature of pigment production, suggesting an intertwined relationship with mining and metallurgy.

Effect of grain size on microstructural and magnetic properties of holmium substituted yttrium iron garnets (Y1.5Ho1.5Fe5O12)

Abstract Grain size changes on microstructural and magnetic properties of holmium substituted yttrium iron garnet with x = 1.5, (Y3-xHoxFe5O12) has been discovered in this research work. The influence of grain size via sintering temperature on a sample’s properties in Holmium substituted in YIG (Ho-YIG) samples has been scrutinized experimentally. In this study, Ho-YIG was mechanically alloyed for 2 h with a mixture of yttrium oxide (Y2O3), holmium oxide (Ho2O3) and iron oxide (Fe2O3). Then, the samples were sintered at distinct temperatures at 1000 to 1400 °C with 100 °C increment. The morphology, physical and magnetic properties has been studied in order to comprehend the resulting materials. Single phase cubic garnet structure has been observed without any other crystallographic phase confirmed through XRD spectra. Single phase of Ho-YIG was formed at 1100 °C. FESEM micrographs showed smaller grain size compared to pure YIG reported in literature as the consequences of holmium substitution. The effects of Holmium substitution in permeability values and B–H hysteresis loops were clearly seen since the dominant magnetization process (spin rotation and movement of ease domain walls) has been interrupted by the presence of rare earth element has decreased the permeability and saturation magnetization values. Substitution of Holmium makes YIG as better soft magnetic material which may be used in electronic devices for the microwave region.

Estudio comparativo del uso de diferentes agentes de sacrificio para la producción de hidrógeno mediante fotocatálisis heterogénea utilizando el mineral arena negra como semiconductor

El mineral arena negra es una mezcla de óxidos de hierro (FeO, Fe2O3, Fe3O4), TiO2 y SiO2 dispuestos en una estructura natural, que podría ser utilizado como semiconductor. En este trabajo se evaluó el efecto del agente de sacrificio para la generación fotocatalítica de hidrógeno utilizando este material como catalizador. Para tal fin se evaluó el efecto de variables del proceso tales como tipo de agente de sacrificio (EDTA, Na2SO3 y metanol) normalmente utilizados como donadores de electrones en la reacción fotocatalítica de producción de hidrógeno, pH inicial de la suspensión (3.0, 7.0 y 9.0) y la concentración del sustrato. Estas variaron entre 1.0, 25.0 y 50.0 mM (EDTA, Na2SO3) y 10.0, 30.0 y 50.0% (v/v) para metanol. Bajo las condiciones de reacción evaluadas, los niveles de máxima producción de hidrógeno fueron Na2SO3>EDTA>CH3OH, respectivamente y la máxima producción de hidrógeno se obtuvo con 25.0 mM Na2SO3 en medio ácido (pH 7.0). La degradación de EDTA y simultánea producción de hidrogeno mediante reacción fotocatalítica, se vieron favorecidos a pH 3.0 y una concentración 1.0 mM

One step green synthesis of larvicidal, and azo dye degrading antibacterial nanoparticles by response surface methodology

The present study explored the one step extracellular green synthesis of Iron oxide (FexOy) and manganese oxide nanoparticles (MnNPs) using aqueous extract of Acorus calamus rhizome. The organic chemicals including polyphenol compounds responsible for bio-reduction and stabilization from the polyphenol enriched microwave irradiated aqueous extract of Acorus calamus were studied using GC–MS analysis. Further, their synthesis conditions were optimized using response surface methodology (RSM) and central composite design (CCD) using three variables. The green synthesized Iron oxide and Manganese oxide NPs were characterized by UV, FTIR, XRD, TEM and SEM. Results indicated that the Iron oxide NPs and mixture of iron and manganese NPs showed photocatalytic excellent activities in reducing dyes like methylene blue (0.1%) and Congo red (0.25%) at 0.03% NPs. However, Mn NPs showed moderate activity. On a contrary, manganese showed better larvicidal activity compared to Iron oxide NPs against the phytopathogens commonly affecting the vegetable crops. The present finding showed that high mortality rate at 30 μg/ml concentration of manganese NPs was comparatively interesting. In addition, NPs overall had appreciable activity with P. aeruginosa being more sensitive to Iron oxide NPs (22 ± 2 mm zone of inhibition) and manganese NPs (13 ± 2 mm zone of inhibition) and Iron oxide NPs completely inhibited the growth of A. flavus at 40 μg/ml concentration.